The proposed project is a neuro-psycho-biological investigation of the structure and function of ascending projections of the brainstem reticular formation. Experimental neuroanatomical studies employing autoradiography, peroxidase histochemistry, and experimental degeneration techniques will be used to study the morphology of reticular efferents, as well as the projections of some of the regions (particularly medial thalamus and subthalamus) which receive direct reticular input. Neurophysiological studies using acute and chronic preparations will investigate the effects of electrical stimulation of the reticular formation and medial diencephalon on spontaneous and evoked single units, multiple unit, and gross slow wave activity of the ventrobasal complex of the thalamus. Behavioral experiments will investigate the relation between reticular activation and discrimination performance to centrally applied stimuli in chronically implanted cats. Although a wide variety of techniques and approaches will be employed, the result will be integrated in an attempt toward an overall understanding of the effects of reticular activation on forebrain excitability.